The correct answer is (b).
Sikkim became an Indian state on 26 April 1975. It was the 22nd state of India. The merger was a result of a referendum held in Sikkim on 14 May 1975, in which 97.5% of the voters voted in favor of merger with India.
The merger was controversial, with some people in Sikkim opposing it. However, the Indian government argued that the merger was in the best interests of Sikkim, as it would bring economic development and stability to the state.
The merger of Sikkim with India was a significant event in the history of both countries. It marked the end of Sikkim’s independence and its integration into the Indian Union. The merger also had a significant impact on the people of Sikkim, who were now citizens of India.
The merger of Sikkim with India was a complex and controversial issue. However, it is now an accepted part of the history of both countries.
(a) June 1969: This is incorrect. Sikkim became an Indian state on 26 April 1975, not June 1969.
(c) December 1972: This is incorrect. Sikkim became an Indian state on 26 April 1975, not December 1972.
(d) July 1980: This is incorrect. Sikkim became an Indian state on 26 April 1975, not July 1980.